The present patent application relates to a plastic moulded box, of improved type, having an articulated compactible structure, capable of considerably reducing the box height when the box is stored or not used, thanks to the fact that the walls can collapse inwards until the upper perimeter frame touches the bottom of the box.
More precisely, the box of the invention is of the type comprising a first rectangular upper frame that defines the opening of the box, a second rectangular lower frame that is an integral part of the bottom of the box and four lateral articulated walls, of which the transversal walls can collapse upwards and inwards, while the longitudinal walls fold inwards, being composed of an identical overlapped pair of semi-borders, hinged to the upper and lower frame, respectively, and mutually hinged on their conjunction axis.
The purpose of the present invention is to improve the resistance of the pivoting pins of the longitudinal walls to the lower frame that defines the bottom, under the stress caused by shocks or falls.
In most cases breakage occurs when the box suffers accidental shocks being in compact position, that is with the four lateral walls collapsed inwards and with the upper frame lowered and positioned on the lower frame that defines the bottom.
Breakage is favoured by the compact position because when the longitudinal walls lose their vertical position and lay on the bottom of the box, the longitudinal walls are less rigid and vibrate, being without load.
In other words, the longitudinal walls are more subjected to the inertia discharged on them when the box is closed and suffer an accidental shock, such as, for example, when handling the box and accidentally dropping it on the floor.
Obviously, inertia stresses the pivoting pins of the walls, which are the only connection constraints between the longitudinal walls and the lower frame of the bottom.
The pins are not dimensioned to withstand high shearing or bending stress since their only function is to allow the longitudinal walls of the box to collapse inwards and resist to vertical stress when the box is open.
The purpose of the invention is to make pivoting pins less vulnerable to breakage without overdimensioning them.
The improved box of the invention is characterised by longitudinal partitions protruding from the bottom and located immediately beside the connection hinges between the bottom and the longitudinal walls.
The partitions are shaped and dimensioned in such a way that they can stop the longitudinal walls when the same are folded inwards until they lay on the bottom.
The improved box of the invention is also characterised by the fact that the longitudinal walls have a transversal series of wedge-shaped protuberances, which create friction against the external side of the partitions when the longitudinal wall is folded inwards. Thanks to the interference between the partitions and the wedge-shaped protuberances the longitudinal wall is stopped, thus completely recovering the travel of the hinge.
It can be said that the improved box of the invention is provided with locking means for the longitudinal borders in collapsed position, in order to prevent any possible movement between the longitudinal walls and the bottom, thus relieving the longitudinal walls from any inertial stress in case of external shocks on the bottom.